Equipments:
Samsung Galaxy S2 (International), IPhone 3GS, IPad 2, Macbook Pro > Creative Sound Blaster Digital Music Premium HD
Highs: Bright and detailed highs. Decay at a much later stage, and because of that, you can hear much more, e.g. like the end vibration of cymbals. But also because of this, there's some sibilant due to the extension of the highs compared to UM3X. Different tips help though.
Mids: Westone UM3X is definitely better here. Mids are pretty recessed for these. So this might affect some vocals, especially with the stronger bass, which might drown out the vocals a little.
Lows: This 2 earphones are...

After picking these up from the Sony Store about a year ago, I can say that these are definitely not worth the $350-$400 price tag. Luckily, I picked them up for around $180 and to me, this seems like a more reasonable price for the XBA-4.
I really wanted to like these IEMs a lot more than I actually do. These were primarily going to be my pair for electronic music. I immediately discovered that these work extremely well with electronic house and heavy trap/bass tracks so it definitely hit the spot for me. However, outside of these genres, these earphones do not sound too good in my opinion.
I can immediately sense that the 4 BA drivers do a great job handling its own...

Along with the summary below, I have a review thread comparing the Sony EX1000, 7550, XBA-4 and XBA-40 here:
http://www.head-fi.org/t/608553/review-comparison-two-flagships-pass-in-the-night-sony-xba-4-review-vs-the-mdr-ex1000-updated-with-7550-and-xba-40
BUILD
The XBA-4 has quite a comfortable design. Despite the large size of the earpieces they fit in my ear well and the light weight makes them quite comfortable. However, depending on the shape of your ear the large body may be uncomfortable with your outer ears. I found the elliptical cable tangled quite easily. The XBA-4 is designed to be worn cable down and doesn't work with cable up wear, which means...

Cons: Size, thin and non-removable wires, short nozzles/tips, sound quality is heavily dependent on the source

I have owned the XBA-3 and XBA-1 beforehand and now I own the 1 and 4 only. As far as multi-driver IEMs go I don't think you'll find a more consumer oriented set than the Apple In-ears and the XBA line.
The package includes the earphones, the same fitting kit included with all the rest from the line (4 sizes of standard universal tips, and 3 sizes of "hybrid" tips that have a ring of foam inside the flap of the tip to provide more isolation), magnetic fake leather carrying case like the XBA-3's, and a cord manager. This is pretty much what you would expect for the price and is not as impressive when compared with something like the XBA-1 which are 1/4 the price and include...

Pros: Great treble, bass, vocals are pretty good, good isolation, very comfortable.

Cons: Treble can sparkle due to spike in frequency response at about 6-7khz*, build quality could be better, no shirt clip.

To get the most out of these i use them with normal buds, as the foam ones reduce treble as per usual with foam, without foam in nozzle as it reduces clarity and with the cable over ear because it allows for the earphone to be in a better position.
I bought them from harvey norman for $197 AU, which is cheaper than ebay, hence why i bought them.
For normal retail price (AU $450) they aren't worth it, but for $200? I couldn't buy them quick enough.
My comparison point is my sennheiser ie8's with a sony walkman as a source, so im used to ridiculous bass.
Treble sparkle is annoying, but forgivable.
Seperation is great due to multiple drivers.
Space is...

I'm no audiophile and these are my first audiophile grade headphone(Sony claim it so).
Comfort-It is amazing! I thought a 4 BA with such big housing will cause discomfort but no! I was wrong, it is very comfortable. It comes with 4 hybird eartips and 3 noise isolation. It shouldn't go wrong but I hope it can be a little longer.
Isolation-Pretty good! Isolates much of the noise from the outside.
Sound-It sounds great! Nothing is over powered. The treble is slightly weak thought but if are willing to do some modification on it, it's perfect!
[The mod is perma (once you did it, you can't undo) but it's simple. Remove the foam in the earphones. You might need some tools to remove it. I...

Tested the XBA4 vs. the EX1000. So, this might be not the most fair comparison, but shows where (all?) multiway drivers lacks.
No doubt, there are highs, mids and deep tones, the only thing that's hard fo find is music.
Especially if you like voices and wide / open soundstaging. Compared to the non BA, one way dynamic predecessor top model EX1000, I instantly get hitted by the extreme differs in overall sound quality and musicality.
Even my old Klipsch 2 way BA Custom 3 is much better overall. (also it has a little less base and highs, but it makes emotions / music)
IMHO Sonys new top model XBA4 is a extreme draw...

If i rate the W4 is 10/10, Xba-4 is 8/10. The W4s are Ok at every expect but lie down a setback note from the W4s ability. Only one thing which the Xba-4 is better than the W4 that is: the Xba do not have the zz zzz sibilance sound..
The biggest issue on this new Sony flagship iem is having a freak noise when playing music and the smaller one is no-unique sound signature.

Cons: Bass could be a bit too much for certain musics. Lack of earbud chocies compare to Shure.

Hi I spent sometime at the local Sonystyle demoing these and thought I'd share my n00b impression.
I'll start off with the conclusion for those who don't want to read the full review.
"These are great in-ear-monitor (IEM) with a VERY strong bass presents, with clear and fine detailed mids and treble (highs)!"
The XBA 4 means there are 4 balanced - armature drivers each responsible or the different frequency of music (high, mids, low, ultra low). These are supposed to be compete with well established multi-driver IEMs like Shure SE535(3 driver) and Weston 3/4s(3/4 driver). I personally own a pair of Shure SE535 and have also listened to the Weston 4S. Sony presented a...